1. Field of the Invention
The present invention relates to a light-emitting device in which a transistor is provided in each pixel.
2. Description of the Related Art
Because display devices using light-emitting elements have high visibility, is suitable for reduction in thickness, and do not have limitations on viewing angles, they have attracted attention as an alternative to CRTs (cathode ray tubes) or liquid crystal display devices. Specific structures of active matrix display devices using light-emitting elements differ depending on manufacturers. In general, at least a light-emitting element, a transistor (switching transistor) which controls input of a video signal to a pixel, and a transistor (driving transistor) which controls the amount of current supplied to the light-emitting element are provided in each pixel.
When all the transistors in the pixels have the same polarity, it is possible to omit some of steps for manufacturing the transistors, e.g., a step of adding an impurity element imparting one conductivity type to a semiconductor layer. Patent Document 1 discloses a light-emitting element type display in which transistors included in pixels are all n-channel transistors.